Magnesium-base alloys containing rare earth metals



United States Patent M 3 231 372 MAGNESIUM-BASI J AI LOYS CONTAINING RARE EARTH METALS George S. Foerster, Midland, Mich., assignor to The Dow 3,231,372 Patented Jan. 25, 1966 in that the aluminum content should not at any time exceed the rare earth content and as the amount of rare earth metal used is increased so also is the amount of aluminum. For example, when 0.5 percent misch metal is ice 5 employed, the aluminum content may be about 0.2 perg g xgi Company Mldland Mich" a corporatmn of cent; whereas when about 1 percent didymium is present No Drawing. Filed Sept. 27, 1963, Ser. No. 311,997 about Percent, of aluminum may be employed; and

6 Cl i (CL 75 163) at 2 percent didymium, about 0.6 percent aluminum is indicated.

This invention relates to magnesium-base alloys con- 10 Small amounts of manganese may also be employed taining rare earth metals having improved strength in the magnesium-base alloy of the present invention for properties. enhanced properties within the range of from about 0.1

Though magnesium-base alloys containing various to about 0.6. rare earth metal mixtures such as, for example, misch Improvement of the properties of the magnesium-base metal and didymium retain a higher proportion of their rare earth metal system, particularly in strength, is unphysical properties at elevated temperatures than other expected inasmuch as aluminum added to such a system is magnesium-base alloys, they tend to have low strength normally deleterious. Surprisingly, however, it has been at room temperatures, and thus, correspondingly lower found that the addition of aluminum to such a system strength properties at elevated temperatures, especially with the range of aforesaid and in accordance with the when extruded at either high temperatures or at high present invention is not deleterious but in fact remarkably speeds. improves the room temperature properties of the alloy An object of the present invention, therefore, is to proand its properties at elevated temperatures. vide a magnesium-base alloy containing rare earth metal The following examples serve to further illustrate the having improved physical properties at normal ambient present inveniton. or room temperatures. A related object is to provide such Various alloys in accordance with the present invention an alloy Whose properties are also improved at elevated and others for comparison as blanks were made using temperatures. conventional alloying and melting techniques as prac- The term rare earth metal as used herein refers to ticed in the magnesium art, each having the composition the metals, either singly or mixtures thereof, having indicated in Table 1. These alloys were cast into billets atomic numbers from 57 to 71, inclusive, commonly rewhich were subsequently extruded from a 3 inch conferred to as those in the lanthanide series. tainer of a ram extrusion machine at the speeds indicated The above object and other objects and advantages of into A inch by Ms inch strips, at a temperature of about the invention have surprisingly and unexpectedly been 750 F., followed by ageing for about 24 hours at a temfound obtainable in a magnesium-base alloy containperature Within the range of from about 350 F. to ing rare earth metals by adding particular amounts of about 400 F. aluminum thereto relative to the amount of rare earth The so-prepared strips, as indicated in Table 1, were metal present in the alloy. then tested at room temperature (25 to 28 C.) for per- Accordingly, the alloy of the present invention concent elongation (percent B) (using a 2 inch gauge sists of a magnesium-base alloy comprising an amount length), tensile yield strength (TYS) (at a 0.2 percent within the range of from about 0.2 to about 4.0 weight deviation from the modulus line), compression yield percent of a rare earth metal such preferably for 11- strength (CYS), and tensile strength (TS). The results ample, lanthanum. praseodymium, neodymium, or of these tests under the conditions indicated are shown cerium, or a mixture of rare earth metal such as, for exin Table 1. Examples 1 and 2 therein were aged at ample, misch-metal (MM) or didymium (Di), and an about 350 F., 3 and 4 at 375 F., and 5 and 6 at 400 F. amount of aluminum within the range of from 0.05 to It should be understood that other fabrication means about 0.8 percent by weight. and ageing conditions, including heat treatments, than Optimum room temperature properties are obtained in those employed above can be used with respect to the althe alloy where the rare earth metal content is within loys of the present invention in order to obtain other the range of from about 0.5 to about 2.0 weight percent, and varied properties in said alloys.

Table 1 Magnesium-Base Plus 1,000 p.s.i. 1,000 p.s.i. Extrusion Per- Extrusion Per- Example Speed cent Speed cent Per- Per- Other, Perf.p.m. E TYS CYS TS t'.p.m. E TYS CYS Ts cent cent Mn cent Di MM A1 20 21 14 12 30 100 12 18 11 35 20 1e 26 19 as 100 14 23 14 37 20 6 2s 12 40 100 6 30 12 42 10 2s 14 15 a3 2o 12 13 a5 10 14 2s 26 3s 50 14 2s 21 39 10 8 27 14 40 90 9 2s 14 40 10 24 14 14 35 25 30 12 13 37 10 24 22 20 36 so 24 17 17 3s 10 10 36 25 41 50 10 30 16 41 1 F.p.m.=feet per minute. 2 P.s.i.=pounds per square inch.

and the amount of aluminum is from about 0.2 to about From the figures in the examples given in Table 1 above 0.6 weight percent. compared to those for the blanks, the improved strength It is preferable to gauge the amount of aluminum in the alloy in accordance wiht the amount of rare earth properties of the alloys representative of the present invention are clearly illustrated.

Among the advantages of the alloy are that it has the light weight characteristic of magnesium, and a high strength to weight ratio, particularly at elevated temperatures and is composed of relatively small amounts of metals, those most preferred being readily available.

The term magnesium as used herein refers to the pure and commercial metal having less than about 0.3 percent of other constituentsv therein either as additives or as unavoidable impurities.

What is claimed and desired to be secured by Letters Patent is:

1. A magnesium-base alloy consisting essentially of rare earth metal in an amount by Weight within the range of from about 0.2 to about 4.0 percent, and aluminum in an amount by weight within the range of from about 0.05 to about 0.8 percent, the balance being essentially magnesium, with the amount of aluminum employed not exceeding that of the rare earth metal.

2. The magnesium-base alloy of claim 1 wherein the rare earth metal is one selected from the group consisting of lath-anum, praseodymium, neodymium, and cerium.

3. The magnesium-base alloy of claim 1 wherein the rare earth metal is present in an amount by weight within the range of from about 0.5 to about 2.0 percent andaluminum is in an amount within the range of from about 0.2 to about 0.6 percent.

4. The magnesium-base alloy of claim 3 wherein the rare earth metal employed is misch metal.

5. The magnesium-base alloy of claim 3 wherein the rare earth metal employed is didymium.

6. The magnesium-base alloy of claim 1 including an amount of manganese within the range of from about 0.1 to about 0.6.

References Cited by the Examiner UNITED STATES PATENTS 2,221,319 11/1940 Altwicker et a1. 75-168 2,801,166 8/1957 Lucien et a1 75-168 DAVID L. RECK, Primary Examiner. 

1. A MAGNESIUM-BASE ALLOY CONSISTING ESSENTIALLY OF RARE EARTH IN AN AMOUNT BY WEIGHT WITHIN THE RANGE OF FROM ABOUT 0.2 TO ABOUT 4.0 PERCENT, AND ALUMINUM IN AN AMOUNT BY WEIGHT WITHIN THE RANGE OF FROM ABOUT 0.05 TO ABOUT 0.8 PERCENT, THE BALANCE BEING ESSENTIALLY MAGNESIUM, WITH THE AMOUNT OF ALUMINUM EMPLOYED NOT EXCEEDING THAT OF THE RARE EARTH METAL. 